The financial support of terrorists is considered what?

The financial support of terrorists is accurately referred to as "financial support to terrorists" because it directly describes the act of providing monetary resources to individuals or organizations engaged in terrorist activities. This terminology encompasses the various ways funding can be channeled to facilitate terrorist operations, whether it's for logistical support, training, or executing attacks.

While the other options contain relevant concepts, they lack the specificity that the correct answer provides. "Supportive action" is broader and does not specifically denote the financial aspect. "Criminal financing" is a term that could apply to various illegal activities beyond terrorism and does not explicitly categorize the funding as related to terrorist efforts. Lastly, "illegal activity" is also a general classification that fails to specify the nature of the act being committed, which in this context centers specifically on providing financial backing to terrorists. Thus, the selected answer is most precise and relevant to the context of the question.